Home /
T.O.C.
FAQs
 
Good
Books
Ref.
Libr.
Advertise
Here
Help
Wanted
Current
Q&A's
Search 🔍
the Site

Chime right in! (no registration req'd)

-----

"Why does chromic acid anodize have excessive white powder residue after DI sealing"





March 4, 2010

Recently we have had some issues with our Chromic Acid Anodize after sealing in DI water. We have checked our test specimens after anodize prior to sealing and they exhibit no evidence of white powder and rough surface. We have tried sealing for less time and at lower temperatures but still have white powder and surface roughness. When we wipe the powder off the surface is shiny and smooth. Our TDS, temp, conductivity etc are all within limits. Corrosion resistance of panels are excellent but paint adhesion will be an issue without wiping every part we process. Any suggestions?

Lynn O'Laney
Employee/QCT - Victoria, BC, Canada
^


March 8, 2010

Alcoa's 1956 Aluminite book reports that over 10 minutes in plain D I water does degrade the coating, that this degradation can be prevented by the addition of a small amount of chromic acid. Email back to me and I will FAX you that part of their book. One of my regular clients has given up trying to seal chromic acid anodizing in plain hot water and is switching to Boeing's idea of 25 gm/100 gal Chromic Acid with 18 gm per 100 gal of Sodium Chromate. There are many commercial specs out there that call for hot water sealing of chromic acid anodizing, but it does not work, especially if you stay in the 15 minutes that the Mil spec calls for. Again Alcoa says limit to 10 minutes to prevent degrading the coating.

robert probert
Robert H Probert
Robert H Probert Technical Services
supporting advertiser
Garner, North Carolina
probertbanner
^

none
finishing.com is made possible by ...
this text gets replaced with bannerText
spacer gets replaced with bannerImages

Q, A, or Comment on THIS thread SEARCH for Threads about ... My Topic Not Found: Start NEW Thread

Disclaimer: It's not possible to fully diagnose a finishing problem or the hazards of an operation via these pages. All information presented is for general reference and does not represent a professional opinion nor the policy of an author's employer. The internet is largely anonymous & unvetted; some names may be fictitious and some recommendations might be harmful.

If you are seeking a product or service related to metal finishing, please check these Directories:

 
Jobshops
Capital
Equipment
Chemicals &
Consumables
Consult'g, Train'g
& Software


About/Contact    -    Privacy Policy    -    ©1995-2021 finishing.com, Pine Beach, New Jersey, USA